1. Field of the Invention
The present invention relates generally to semiconductor devices having a metallic shielding plate to protect a semiconductor chip from magnetism. More particularly, the invention is directed to a semiconductor device capable of preventing a semiconductor chip from becoming damaged by contact with any burrs formed at edges of a metallic shielding plate during cutting thereof. The invention also concerns a method of manufacturing a metallic shielding plate used in a semiconductor device including a semiconductor chip and a resin for sealing the semiconductor chip, the metallic shielding plate protecting the semiconductor chip from external magnetism.
2. Description of the Related Art
Semiconductor devices with a semiconductor chip such as a magnetoresistive random-access memory (MRAM) contain a metallic shielding plate in the device. In order to protect the semiconductor chip of a semiconductor device from the magnetism (magnetic fields) entering from the outside of the semiconductor device, such a metallic shielding plate is fabricated from a metallic material having a magnetic shielding effect.
A metallic shielding plate would be fabricated by machining a metallic material using a press. The metallic shielding plate thus completed, however, will have machining burrs or rough edges and suffer deformation, and in such a case, the burrs have tended to damage the circuits of the semiconductor chip due to contact with the circuit surface of the chip. Accordingly, the fabrication of a metallic shielding plate by press machining has been problematic.
For this reason, it has been common to fabricate metallic shielding plates using an etching method. Among conceivable etching methods is single-side etching, in which method, individual metallic shielding plates will be fabricated by first providing a metallic material that includes a taping material attached to one surface, and then etching the metallic material from the surface side opposite to the particular surface. The single-side etching method, however, has the problem that it requires an etching time nearly twice as much as a metallic shielding plate is fabricated by etching both sides of a metallic material at the same time. Single-side etching method has another problem in that since the etched section will have a shape tapered off to one side, the shielding effect at the edges of the metallic shielding plate will decrease.
Patent Document 1: JP-A-9-130082